The image has come to symbolize the chaos and carnage of war: A panic-stricken horse, impaled by a spear, whose death-dance dominates the center of Pablo Picasso’s Guernica. Man’s inhumanity to man is a fundamental trope in the discourse of war—and one we can grow all too quickly numb to. But evidence of the widespread suffering of animals—in World War I accounts of biological agent testing, or the massacre at Tokyo’s Ueno Zoo in 1943—provides a different, and necessary, kind of shock, and a reminder that the damage inflicted by war is not limited to humans.

The National Theatre of Great Britain's production of WAR HORSE valiantly attempts to make a wartime epic out of a 1982 children's novel of the same name, in which novelist Michael Morpungo sought to view the First World War through the eyes of a horse and those closest to him.

To do this, it embraces spectacle. And Christopher Shutt and John Owens' sudden sound effects, Paule Constable and Karen Spahn's piercing lights, Adrian Sutton's alarm-filled score and Rae Smith's affecting illustrations, animated by 59 Productions and projected along what appears to be a stage-long piece of torn manuscript above the actors, all effectively convey the horrors of the battlefield.

Meanwhile, the cunningly engineered and remarkably animated two- and three-person puppets devised by South Africa's Handspring Puppet Company convey the strain and the terror of the title character, a hunter thoroughbred named Joey, and another horse named Topthorn, as they try to drag a field gun through a battlefield's mud.

But when this production focuses on humans, and not animals, the script's weaknesses start to show.

Nick Stafford's adaptation repeatedly sacrifices depth for breadth, simplifying a series of characters to little more than primary traits. By this, Ted (Todd Cerveris), the father of the (human) hero is reduced to an alcoholic bully, while Friedrich (Andrew May), a German captain who saves Joey's life, is crayoned down to a nice guy who, when caught on the wrong side, obligingly deserts at the first opportunity.

The script picks up—and then abandons—Lavita Shaurice's poignant Emilie and Megan Loomis' Paulette, before it jettisons the rest of the war after the inevitable reunion of horse with Albert (Andrew Veenstra), the Devon boy who first loved him, in an unseemly race to get to the happy ending.

When a show works, we don't feel this manipulated. War Horse tugs at our heartstrings—and pushes our buttons—as it presents a truly harrowing view of a battlefield.

But when the animals are more thoroughly characterized than a number of the humans, something's missing: A script written for—and populated by—fully dimensional adults.